1. Field of the Invention
The invention relates to a cutting unit for agricultural machines according to the preamble part of claim 1.
The cutting unit of a baler, in particular, a round baler, has to cut crop material, e.g. supplied by a pick-up device and to convey the cut crop material into a bale forming cavity. The cutting unit of a loading wagon has to cut the crop material, e.g. supplied by a pick-up device and to convey the cut crop into a storage hopper of the loading wagon. The tine arrangements take the supplied crop and force the crop over the cutting blades, which cut the crop material into smaller pieces. During and/or after the cutting process, the scrapers remove the cut crop material from the tine arrangements and guide it further in conveying direction through the conveying channel. In the case of e.g. round balers, the conveying channel has an inlet and an outlet, which are substantially in-line with each other, such that each of the tines engages into the crop material over a rotation of the rotor of about 180°. In the case of the loading wagon, the outlet of the conveying channel may extend upwardly, such that the tines engage into the crop material over an angular range of about 270°.
2. Description of the Related Art
The example of a cutting unit of a round baler known from EP 0815720 A has a plurality of axially spaced apart, parallel tine arrangements on the base body of the rotor. A circumferential phase shift is provided between adjacent tine arrangements. Each tine arrangement consists of two ring structures each having two diametrically opposed triangular tine tips. The cutting blades either engage between the ring structures and/or between and/or at the side or sides of the ring structures. The tines provided are so-called low-base tines, meaning that each tine has a triangular tine tip and a low-base extending, e.g. to both circumferential sides of the tine tip. The base firmly secures the tine to the periphery of the base body of the rotor. The constant distance of the outer contour of the low-base from the axis of the rotor e.g. amounts to about half of the radial distance of the tine end from the axis. An advantage of a low-base tine is that the rotor with the low-base tines facilitates to process a high flow rate of crop material in the cutting unit. However, in particular, in a cutting unit, where the crop material supplying direction is almost in line with the outlet direction from the conveying channel, as e.g. in most round balers, the crop material conveyed by each tine may markedly be pressed against the scraper before cutting a cutting blade, or in case of a cutting blade having a steep cutting edge the crop material will be pressed by the tine tip almost perpendicularly against the cutting edge. Moreover, the crop material mainly is cut with a squeezing cutting action on the cutting edge of the cutting blades, because the outer contour of the base remains passive, while the crop material is forced by the tine tip and the scrapers only against the cutting edge substantially perpendicular to the curvature of the cutting edge. Squeezing cutting actions require much rotor driving energy, results in poor quality of the cut crop material, and causes locally concentrated wear of the cutting edges of the cutting blades.
Instead of low-base tines, it is know in practice to equip rotors of cutting units with so-called high-base tines. There the constant radial distance of the outer contour of the base situated ahead of a tine tip in the direction of rotation of the rotor is constant and may amount to about two-thirds of the radial distance of the tine tip end from the axis of the rotor. An advantage of high-base tines is that the cutting action on each cutting blade is executed better than with a low-base tine, meaning that the crop material, while being cut, somewhat slides along the cutting edge of the cutting blade. The improved cutting action results in less rotor driving energy and less squeezing of the crop material. However, high-base tines cannot convey as much crop material as low-base tines, and undesirably restrict the crop material flow rate through the cutting unit.
Further prior art cutting units are disclosed in EP 659 332 A, EP 148 537 A, and EP 64112 A.
In recent years the capacity of such cutting units had to be increased due to the increased processing capacity of e.g. round balers or the demand to fill a large capacity loading wagon rapidly. The crop material flow rate capacity of cutting units was mainly increased by increasing the active diameter of the rotor. However, this results in problems in agricultural machines where the mounting space for the cutting unit is limited. Increasing the rotor diameter also automatically needs higher rotor driving torque, more robust frame structures, results in a higher total weight of the machines, and higher manufacturing costs.